Organization and Business (Details 2) $ in Thousands, T in Millions	9 Months Ended
	Sep. 30, 2015 USD ($) T	Sep. 30, 2014 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payments made upon signing JV agreement | $		$ 0
Payments to fund permitting expenses in GPT | $	$ 5,383	$ 0
GPTJointVenture [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Future Nonbinding Commitments To Fund Joint Venture | $	$ 30,000
Joint venture ownership percentage	49.00%
Permitting costs paid | $	$ 2,000
Permitting cost sharing agreement	Thereafter, the owners will share any permitting expenses in excess of $30 million in proportion with their ownership interests.
CrowTribe [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option to purchase investment in equity method investee	5.00%
SSA Marine [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Equity method investment remaining percentage	51.00%
Westshore | Equal to or less than | Committed Capacity 2015 [Member] | 2015 Exports
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Committed Capacity	4.3
Committed Capacity Adjustment	1.9
Third Party Tons Sold	4.0
Millennium | Equal to or less than
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Throughput Option	7.7
SSA Marine [Member] | Equal to or less than
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Throughput Option	17.6